It is known that monomers, such as ethylene, propylene, and other olefins, may be polymerized at various temperatures and pressures. Depending on the type of polymerization process, the polymerization process pressure range may be from around 0.1 MPa to over 300 MPa and the temperature can range from about 40° C. to in excess of 300° C.
More specifically, with regard to solution polymerization, the polymerization pressure range may be from about 0.1 MPa to about 15 MPa and at a temperature of about 40° C. to about 225° C. Solution polymerization involves dissolving a monomer, such as ethylene, in a solvent and heating the dissolved mixture in a reactor under pressure in the presence of a catalyst, thereby inducing the polymerization process. Furthermore, solution processes are operated at temperatures that exceed the melting or solubilization temperature of the polymer that is produced. The solution process is operated so that both the monomer and the polymer are soluble in the reaction medium.
Exemplary of solution polymerization reactions are disclosed in the following references: U.S. Pat. No. 5,589,555 to Zboril et al., U.S. Pat. No. 5,151,474 to Lange et al., U.S. Pat. No. 4,469,853 to Mori, U.S. Pat. No. 3,725,378 to Chamberlin, and U.S. Pat. No. 4,175,169 to Beals et al.
Conventional means of controlling the polymerization process involve monitoring the physical properties of the reactive mixture within the reactor and the product stream downstream of the reactor. Typically a sample from the polymerization process is taken, however, such sampling activities are time intensive and such results are typically only available every 2 to 4 hours. With regard to commercial scale polymerization processes, many thousands of tons of product can be produced in the time span of 2 to 4 hours. As such, this sampling delay might allow a very large amount of product to be produced that is out of specification.